$ { \left[\begin{array}{rr}{1} & {-2} \\ {-1} & {-1} \\ {-1} & {4}\end{array}\right]-\left[\begin{array}{rr}{3} & {4} \\ {0} & {-1} \\ {1} & {2}\end{array}\right] = {?} } $
Answer: To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{rr}{1}-{3} & {-2}-{4} \\ {-1}-{0} & {-1}-{-1} \\ {-1}-{1} & {4}-{2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{-2} & {-6} \\ {-1} & {0} \\ {-2} & {2}\end{array}\right]}$